1. Field Of The Invention
This invention relates generally to pavement markers, and is particularly concerned with pavement markers constructed in such a way as to have high resistance to being damaged or displaced by snow plows and similar equipment.
2. Description Of The Prior Art
It has become common practice to delineate traffic lanes and the edges of roadways by pavement markers having retro-directive reflector elements or other reflecting material for reflecting the lights from vehicles traveling over the roadways at night. Such pavement markers are superior to painted strips on the roadways, since, under poor weather conditions, painted strips on the roadway are not visible.
A particular problem with pavement markers in colder climates is that the pavement markers are frequently subjected to damage and displacement by snow plows and similar road equipment. Typically, the pavement markers are secured to the surface of the roadway by an adhesive, such as an epoxy resin. If the pavement marker projects from the surface of the roadway at an abrupt angle, it is easily damaged or displaced when struck by a snow plow.
Several approaches have been taken in the prior art to provide resistance to damage by snow plows. One such approach is to mount the pavement marker in a recess in the roadway, and to resiliently support the pavement marker in the recess so that the pavement marker yields when engaged by a vehicle or the like. See, for example, U.S. Pat. Nos. 2,981,149 and 3,502,008. Another approach is to provide a heavy metal frame for the pavement marker. See, for example, U.S. Pat. Nos. 2,034,391; 1,849,419; 2,094,652; and 3,784,279.
Typical examples of reflective pavement markers are disclosed in U.S. Pat. Nos. 3,332,327; 3,409,344 and 3,516,337. The latter patents disclose pavement marker bodies having retro-directive reflector elements formed thereon, such as cube corner reflex reflector elements. In order to protect the cube corner reflector elements from moisture and chemical attack, the surface of the reflector elements are metallized. While the metallized layer performs the function of protecting the reflector elements, it also causes a loss of optical efficiency.